In conventional image forming apparatus, only a paper discharge detecting sensor has been used for a decision on a paper jam. That is to say, it has been a known practice that unless a paper discharge detecting sensor becomes a sensing state within a predetermined time the conveyance of a paper sheet is stopped as a result of a judgment of a non-arrival jam, and that unless the paper discharge detecting sensor becomes a non-sensing state within a predetermined time the conveyance of the paper sheet is stopped as a result of a judgment of a stagnating jam.
Also, it has been a known practice that with a fullness detecting sensor provided for detecting a fullness of the paper sheets on a paper receiving tray apart from the paper discharge detecting sensor a control section makes a judgment of fullness if the fullness detecting sensor remains in the sensing state more than a predetermined time, and that the conveyance of the paper sheet is stopped thereby.
However, providing the paper discharge detecting sensor and the fullness detecting sensor provided together requires improved accuracy on respective components related, which has resulted in cost increase.
Then, an image forming apparatus has been disclosed in which detection of whether or not the paper sheet is discharged onto the paper receiving tray and detection of whether or not the paper sheets discharged onto the paper receiving tray are full are carried out by a single sensing device (for example, refer to Patent Literature 1).